[PATCH] ntfs: do not dereference a null ctx on error

[Nickolai Zeldovich <nickolai@csail.mit.edu>]

In ntfs_mft_data_extend_allocation_nolock(), if an error condition occurs
prior to 'ctx' being set to a non-NULL value, avoid dereferencing the NULL
'ctx' pointer by jumping to later cleanup code.

Signed-off-by: Nickolai Zeldovich <nickolai@csail.mit.edu>
---
 fs/ntfs/mft.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ntfs/mft.c b/fs/ntfs/mft.c
index 3014a36..e6ea11c 100644
--- a/fs/ntfs/mft.c
+++ b/fs/ntfs/mft.c
@@ -1822,13 +1822,13 @@ static int ntfs_mft_data_extend_allocation_nolock(ntfs_volume *vol)
 	if (IS_ERR(mrec)) {
 		ntfs_error(vol->sb, "Failed to map mft record.");
 		ret = PTR_ERR(mrec);
-		goto undo_alloc;
+		goto undo_alloc_noctx;
 	}
 	ctx = ntfs_attr_get_search_ctx(mft_ni, mrec);
 	if (unlikely(!ctx)) {
 		ntfs_error(vol->sb, "Failed to get search context.");
 		ret = -ENOMEM;
-		goto undo_alloc;
+		goto undo_alloc_noctx;
 	}
 	ret = ntfs_attr_lookup(mft_ni->type, mft_ni->name, mft_ni->name_len,
 			CASE_SENSITIVE, rl[1].vcn, NULL, 0, ctx);
@@ -1988,8 +1988,8 @@ undo_alloc:
 				"context.%s", es);
 		NVolSetErrors(vol);
 	}
-	if (ctx)
-		ntfs_attr_put_search_ctx(ctx);
+	ntfs_attr_put_search_ctx(ctx);
+undo_alloc_noctx:
 	if (!IS_ERR(mrec))
 		unmap_mft_record(mft_ni);
 	up_write(&mft_ni->runlist.lock);
-- 
1.7.10.4